Prostheses for the repair of vascular defects, including for example vascular aneurysms, are well known in the art. A common prosthesis for treatment of such a medical condition is a stent graft. It is also known to provide such prostheses in modular form, for example when it is necessary for the prosthesis to straddle a plurality of vessels, such as the superior mesenteric artery and the iliac arteries. Similarly, a modular prosthesis may be provided in cases where the dimensions of the artery or other vessel to be treated would vary substantially from one end of the prosthesis to the other. Yet another example is where a medical condition necessitates the use of different types of prosthesis along the length of the site to be treated.
It is common for such modular prostheses to be coupled together by nesting one section within the other and expanding the innermost section against the interior surface of the outer section. Such expansion can be effected, for example, by means of a self-expanding element such as a self-expanding stent, or by a separate expansion mechanism, such as an expandable balloon. It will be apparent that in order to obtain a fluid-tight seal between the various modules of such a prosthesis the sections must have complementary dimensions at their point of coupling. This necessitates careful manufacturing and imposes consequential limitations on the design of the modules.
Furthermore, it is necessary in many medical treatments, such as in the treatment of aneurysms, the bypass of occluded or otherwise damaged vessels and so on, to provide a fluid-tight seal between the ends of the prosthesis and the walls of the vessel in order to avoid blood loss. This requires the prosthesis, for example the stent-graft, to be of a suitable dimension for the particular vessel being treated. As a result of this, a surgeon must select a suitable prosthesis size for the dimensions of the vessel as well as for the particular vessel characteristics at the place of implantation of the prosthesis. Particular problems can arise in the case of aneurisms, for example, where the vessel is enlarged at the ends of the prosthesis or at the point of coupling of two modules of a modular prosthesis.